1. Field of the Invention
This invention relates in general to a computer-implemented database system, and more particularly, to explaining data using a graphical user interface.
2. Description of Related Art
Databases are computerized information storage and retrieval systems. A Relational Database Management System (RDBMS) is a database management system (DBMS) which uses relational techniques for storing and retrieving data. Relational databases are organized into tables which consist of rows and columns of data. The rows are formally called tuples. A database will typically have many tables and each table will typically have multiple tuples and multiple columns. The tables are typically stored on random access storage devices (RASD) such as magnetic or optical disk drives for semi-permanent storage.
RDBMS software using a Structured Query Language (SQL) interface is well known in the art. The SQL interface has evolved into a standard language for RDBMS software and has been adopted as such by both the American National Standards Institute (ANSI) and the International Standards Organization (ISO). The SQL interface allows users to formulate relational operations on the tables either interactively, in batch files, or embedded in host languages, such as C and COBOL. SQL allows the user to manipulate the data.
The definitions for SQL provide that a RDBMS should respond to a particular query with a particular set of data given a specified database content, but the method that the RDBMS uses to actually find the required information in the tables on the disk drives is left up to the RDBMS. Typically, there will be more than one method that can be used by the RDBMS to access the required data. The RDBMS will optimize the method used to find the data requested in a query in order to minimize the computer time used and, therefore, the cost of doing the query.
The RDBMS software uses various data, including statistics in a RDBMS catalog, during bind time to determine the access paths of SQL statements. A utility, called RUNSTATS, updates the RDBMS catalog with statistics on table spaces, indexes, tables, and columns. Additionally, when an SQL statement is processed during a bind phase, an access path is determined for the statement. The access path is a compiled run-time structure used for executing the SQL statement. The access path is the path the RDBMS uses to get to the data that SQL statements request. For example, an SQL statement might search an entire table space, or it might use an index. The access path is the key to determining how well an SQL statement performs. The data associated with the access path is stored in the DB2 directory, or optionally in a plan table. The plan table holds information about a plan, which is a set of one or more programs or is a portion of a program.
Analyzing and improving performance of SQL statements is currently too time-consuming and complex for the average user. In a conventional system, a user typically improves performance of SQL statements by determining the access path for a SQL statement by manually interpreting data in the plan table that holds data associated with the access path. Moreover, in conventional systems, although data in a plan table is available on a mainframe, it is in a format that is difficult to understand and must be interpreted by the user. Therefore, conventional systems do not offer users at workstations access to databases on a mainframe for obtaining data in the plan table that is easy to understand. There is a need in the art for providing users at workstations access to this information from the mainframe and providing an improved technique for users to optimize access paths.
Additionally, the RDBMS has subsystem parameters that describe the values of user set options, such as the number of current users and number of open datasets allowed at one time. Conventional systems do not provide an easy way to display and find the values, install field names, and descriptions of the subsystem parameters. There is a need in the art for an improved technique that allows a user to view subsystem parameters.